Multiple Group One winner Tepin has been retired after losing her enthusiasm for racing.

Winner of the Breeders' Cup Mile in 2015 and twice the United States champion mare on turf, she was narrowly beaten on what was her final career start when she attempted to defend the race at Santa Anita in November.

The six-year-old's finest hour was at Royal Ascot last year when Mark Casse's stable star overcame the long journey from North America and the soft ground to claim the Queen Anne Stakes.

Owner Robert Masterson said she had simply lost interest in racing.

""There is nothing physically wrong with her. She just isn't interested in running any more," Masterson told Thoroughbred Daily News.

"There are no plans to breed her this year. It's too late, and we've not made any decision on her future.

"She was always an enthusiastic worker, and enthusiastic in the mornings and about racing, and she is not any more."